The Childhood Obesity Epidemic

Metformin reduces insulin resistance and attenuates progressive renal injury in prepubertal obese Dahl salt-sensitive rats

Prepubertal obesity is currently an epidemic and is considered as a major risk factor for renal injury. Previous studies have demonstrated that insulin resistance contributes to renal injury in obesity, independent of diabetes. However, studies examining the relationship between insulin resistance and renal injury in obese children are lacking. Recently, we reported that progressive renal injury in Dahl salt-sensitive (SS) leptin receptor mutant (SSLepRmutant) rats was associated with insulin resistance before puberty. Therefore, the aim of the present study was to examine whether decreasing insulin resistance with metformin will reduce renal injury in SSLepRmutant rats. Four-wk-old SS and SSLepRmutant rats were separated into the following two groups: 1) vehicle and 2) metformin (300 mg/kg/day) via chow diet for 4 wk. Chronic administration of metformin markedly reduced insulin resistance and dyslipidemia in SSLepRmutant rats. We did not detect any differences in mean arterial pressure between vehicle and metformin-treated SS and SSLepRmutant rats. Proteinuria was significantly greater in SSLepRmutant rats versus SS rats throughout the study, and metformin administration significantly reduced proteinuria in SSLepRmutant rats. At the end of the protocol, metformin prevented the renal hyperfiltration observed in SSLepRmutant rats versus SS rats. Glomerular and tubular injury and renal inflammation and fibrosis were significantly higher in vehicle-treated SSLepRmutant rats versus SS rats, and metformin reduced these parameters in SSLepRmutant rats. These data suggest that reducing insulin resistance with metformin prevents renal hyperfiltration and progressive renal injury in SSLepRmutant rats before puberty and may be therapeutically useful in managing renal injury during prepubertal obesity.NEW & NOTEWORTHY Childhood/prepubertal obesity is a public health concern that is associated with early signs of proteinuria. Insulin resistance has been described in obese children. However, studies investigating the role of insulin resistance during childhood obesity-associated renal injury are limited. This study provides evidence of an early relationship between insulin resistance and renal injury in a rat model of prepubertal obesity. These data also suggest that reducing insulin resistance with metformin may be renoprotective in obese children.

[Flow mediated vasodilation in overweight children]

INTRODUCTION

Present knowledge suggests that cardiovascular disease originates and progresses from childhood and adolescence. Endothelial dysfunction is an early and crucial event in atherosclerosis.

PATIENTS AND METHOD

Prospective study that compares Flow Mediated Vasodilation (FMV) in children with overweight (OWC) and normal weight children. An ultrasound transducer a standard method were used to measure FMD.

RESULTS

The study included 82 children, of whom 49 were cases (OWC) and 33 controls. FMV values ranged from -6 to 56% (x=11.1%) in OW, and from 0 to 29.6% (x=16.6%) in control children (P<.005). Paradoxical vasoconstriction was found in 34.7% in OWC as compared to nil in controls (P<.005). A significant association was found between vasoconstriction and central obesity and hypertension.

CONCLUSION

The results of this study show that FMV is lower in obese compared to normal children; thus they are more likely to have endothelial dysfunction.

Metabolic risk in contemporary children is unrelated to socio-economic status: longitudinal study of a UK urban population (EarlyBird 42)

Lifestyle interventions to improve health in young children tend to target areas of relative deprivation, but the evidence for so doing is largely historical. Accordingly, we have re-examined the link between deprivation, obesity and metabolic risk in contemporary UK children. Using a postcode-based index of multiple deprivation (IMD), we assessed 269 children from the community-based EarlyBird Study, attending 53 schools representing a wide socio-economic range. Annual measures of fatness from 5 to 8 yr included body mass index (BMI), waist circumference (WC), and sum of five skinfolds (SSF). A metabolic risk score, based on blood pressure, lipids and insulin resistance, was derived from annual fasting blood samples. There were no significant associations between deprivation and any measure of adiposity in girls (all p > 0.37). In boys, there was a weak but consistently inverse relationship between deprivation and WC (r = -0.19, p = 0.03) and BMI (r = -0.14, p = 0.09) at 8 yr. Changes in adiposity over 3 yr were unrelated to deprivation in boys. In girls there was a slight but significant increase in SSF only (1 mm/yr per 20 IMD units, p = 0.001). Importantly, in both genders, metabolic risk score was unrelated to deprivation throughout (r values -0.05 to -0.13, all p > 0.12), as was change in metabolic risk (all p > 0.30). Our data do not support the assumption that obesity, metabolic disturbance and thus risk of type 2 diabetes are more prevalent among poorer children. In today's increasingly obesogenic environment, youngsters from all backgrounds appear to be vulnerable, with population-wide implications for public health spending, and the prevention of diabetes in contemporary youth.

Brachial artery adaptation to lower limb exercise training: role of shear stress

Lower limb exercise increases upper limb conduit artery blood flow and shear stress, and leg exercise training can enhance upper limb vascular function. We therefore examined the contribution of shear stress to changes in vascular function in the nonexercising upper limbs in response to lower limb cycling exercise training. Initially, five male subjects underwent bilateral brachial artery duplex ultrasound to measure blood flow and shear responses to 30-min cycling exercise at 80% of maximal heart rate. Responses in one forearm were significantly (P < 0.05) attenuated via cuff inflation throughout the exercise bout. An additional 11 subjects participated in an 8-wk cycle training study undertaken at a similar intensity, with unilateral cuff inflation around the forearm during each exercise bout. Bilateral brachial artery flow-mediated dilation responses to a 5-min ischemic stimulus (FMD%), an ischemic handgrip exercise stimulus (iEX), and endothelium-independent NO donor administration [glyceryl trinitrate (GTN)] were measured at 2, 4, and 8 wk. Cycle training increased FMD% in the noncuffed limb at week 2, after which time responses returned toward baseline levels (5.8 ± 4.1, 8.6 ± 3.8, 7.4 ± 3.5, 6.0 ± 2.3 at 0, 2, 4 and 8 wk, respectively; ANOVA: P = 0.04). No changes in FMD% were observed in the cuffed arm. No changes were evident in response to iEX or GTN in either the cuffed or noncuffed arms (P > 0.05) across the 8-wk intervention period. Our data suggest that lower limb cycle training induces a transient increase in upper limb vascular function in healthy young humans, which is, at least partly, mediated via shear stress.

Aerobic interval training reduces cardiovascular risk factors more than a multitreatment approach in overweight adolescents

The aim of the present study was to compare the effects of a multidisciplinary approach (MTG) and aerobic interval training (AIT) on cardiovascular risk factors in overweight adolescents. A total of 62 overweight and obese adolescents from Trøndelag County in Norway, referred to medical treatment at St Olav's Hospital, Trondheim, Norway, were invited to participate. Of these, 54 adolescents (age, 14.0 +/- 0.3 years) were randomized to either AIT (4 x 4 min intervals at 90% of maximal heart rate, each interval separated by 3 min at 70%, twice a week for 3 months) or to MTG (exercise, dietary and psychological advice, twice a month for 12 months). Follow-up testing occurred at 3 and 12 months. VO(2max) (maximal oxygen uptake) increased more after AIT compared with MTG, both at 3 months (11 compared with 0%; P<0.01) and 12 months (12 compared with -1%; P<0.01). AIT enhanced endothelial function compared with MTG at both 3 months (absolute change, 5.1 compared with 3.9%; P<0.01) and 12 months (absolute change, 6.3 compared with 1.0%; P<0.01). AIT was favourable compared with MTG in reducing BMI (body mass index), percentage of fat, MAP (mean arterial blood pressure) and increasing peak oxygen pulse. In addition, AIT induced a more favourable regulation of blood glucose and insulin compared with MTG. In conclusion, the novel findings of the present proof-of-concept study was that 3 months of twice weekly high-intensity exercise sessions reduced several known cardiovascular risk factors in obese adolescents more than that observed after a multitreatment strategy, which was initiated as hospital treatment. Follow-up at 12 months confirmed that AIT improved or maintained these risk factors to a better degree than MTG.

Relationships between measures of fitness, physical activity, body composition and vascular function in children

BACKGROUND

The prevalence of obesity and physical inactivity in Western countries has increased rapidly. Both are modifiable risk factors for cardiovascular disease. Atherosclerosis begins in childhood and endothelial dysfunction is its earliest detectable manifestation.

METHODS

We assessed flow-mediated dilation (FMD) in 129 children (75 female; 10.3+0.3 yrs; 54 male; 10.4; 0.3 yrs). FMD was normalised for differences in the eliciting shear rate stimulus between subjects (SR(AUC)). Fitness was assessed as peak oxygen uptake during an incremental treadmill exercise test (V O(2)peak). Body composition was measured using a dual-energy X-ray absorptiometry (DEXA) scan. Physical activity (PA) was assessed using Actigraph accelerometers. The cohort was split into tertiles according to FMD% and also FMD% corrected for SR(AUC) to gain insight into the determinants of vascular function.

RESULTS

Across the cohort, significant correlations were observed between FMD%/SR(AUC) and DEXA percentage fat (r=-0.23, p=0.009) and percentage lean mass (r=0.21, p=0.008), and also with PA performed at moderate-to-high intensity (r=0.363, p=0.001). For children in the lowest FMD%/SR(AUC) tertile, a stronger relationship with all PA measures was observed, particularly with high intensity PA (r=0.572, P=0.003). Regression analysis revealed that high intensity PA was the only predictor of impaired FMD%/SR(AUC).

CONCLUSIONS

These data suggest that traditional risk factors for CHD in adult populations impact upon vascular function in young people. Furthermore, it appears that individuals with impaired FMD may benefit from performing high intensity PA, whereas no relationships exist between FMD and lower intensities of PA or between PA and FMD in those subjects who possess preserved vascular function a priori.

Rise in childhood obesity with persistently high rates of undernutrition among urban school-aged Indo-Asian children

BACKGROUND

Childhood obesity is an emerging global public health challenge. Evidence for the transition in nutrition in Indo-Asian developing countries is lacking. We conducted these analyses to determine the trends in nutritional status of school-aged children in urban Pakistan.

METHODS

Data on the nutritional status of children aged 5 to 14 years from two independent population-based representative surveys, the urban component of the National Health Survey of Pakistan (NHSP; 1990-1994) and the Karachi survey (2004-2005), were analysed. Using normative data from children in the United States as the reference, trends for age- and gender-standardised prevalence (95% CI) of underweight (more than 2 SD below the weight-for-age reference), stunted (more than 2 SD below the height-for-age reference) and overweight and obese (body mass index (BMI) 85(th) percentile or greater) children were compared for the two surveys. The association between physical activity and being overweight or obese was analysed in the Karachi survey using logistical regression analysis.

RESULTS

2074 children were included in the urban NHSP and 1675 in the Karachi survey. The prevalence of underweight children was 29.7% versus 27.3% (p = 0.12), stunting was 16.7% versus 14.3% (p = 0.05), and prevalence of overweight and obese children was 3.0 versus 5.7 (p<0.001) in the NHSP and Karachi surveys, respectively. Physical activity was inversely correlated with being overweight or obese (odds ratio, 95% CI, 0.51, 0.32-0.80 for those who engaged in more than 30 minutes of physical activity versus those engaged in less than 30 minutes' activity).

CONCLUSIONS

Our study highlights the challenge faced by Pakistani school-aged children. There has been a rapid rise in the number of overweight and obese children despite a persistently high burden of undernutrition. Focus on prevention of obesity in children must include strategies for promoting physical activity.

Physical Activity: The Epidemic of Obesity and Overweight Among Youth: Trends, Consequences, and Interventions

Childhood and adolescent overweight and obesity are an epidemic problem in the United States. Studies show that approximately one third of youth are overweight or obese, representing a tripling since the 1960s and 1970s. The average male and female adult in the United States has gained 25 lbs and 24 lbs, respectively, since 1962. The body mass index of the average adult has increased from 25 to 28. Among youth, the average body mass index has increased from 21.3 to 24.1 since 1963. This increase in bodyweight among adults and youth is partially due to the decreased levels of physical activity. The economic and health consequences of this epidemic are enormous. Type 2 diabetes mellitus, a disease that was rare among youth 20 to 30 years ago, now represents as many as 45% of all cases of diabetes among youth. Cardiovascular risk factors are worsened in overweight and obese youth, and early evidence of atherosclerosis manifested by endothelial dysfunction and increased coronary artery calcium is present in a high percentage of overweight youth. Numerous psychosocial problems also are increased among overweight and obese youth. However, there are numerous examples in the scientific literature of successful approaches to the prevention and management of overweight and obesity in youth. This article summarizes statistics concerning the prevalence of overweight, obesity, and physical inactivity among youth; discusses the numerous physical and psychosocial consequences of overweight and obesity among youth; and presents information regarding interventions that have been demonstrated to be effective in preventing childhood and adolescent overweight and obesity.

Comparing child-feeding practices of Dominican mothers

The purpose of this study was to compare similarities and differences between two samples - mothers of children under the age of 6 years living in the Dominican Republic (D.R.) and recent immigrants from the D.R. to the United States - on their (a) feeding practices for infants and young children, (b) knowledge regarding healthy size and weight and ideal diet for young children, and (c) knowledge regarding the causes and health implications of childhood obesity. An exploratory descriptive design was used, and qualitative data were collected through focus groups.

Endothelial dysfunction in obesity: etiological role in atherosclerosis

PURPOSE OF REVIEW

To review studies of vascular endothelial dysfunction in obesity, discuss potential mechanisms of disease, and address the therapeutic effects of weight loss interventions on arterial health.

RECENT FINDINGS

Endothelial dysfunction represents the earliest abnormality in the development of vascular disease, and is pathophysiologically linked to subsequent atherosclerosis progression and cardiovascular disease events. Obesity is closely associated with a number of established cardiovascular risk factors, including diabetes mellitus, insulin resistance, dyslipidemia, and hypertension that are cumulatively damaging to the endothelium. In addition, there is now a growing recognition of non-traditional risk factors as potential modulators of the endothelial phenotype in obesity, including fat tissue production of proatherogenic adipokines, oxidative stress, and chronic inflammation. Clinical studies have demonstrated that even modest weight loss reverses endothelial dysfunction, and the restoration of arterial homeostasis could potentially reduce cardiovascular risk.

SUMMARY

Obesity is associated with altered arterial homeostasis and endothelial dysfunction. Mechanisms of disease are related to a complex interplay of metabolic and inflammatory factors that coordinately improve along with arterial function in response to weight loss interventions.